According to this link (warning, some gruesome images of dodgy and infected nails!):

"Vertical Ridges are also characteristic of aging, although are not limited to the aged or elderly. The nail plate grows forward on the nail bed in a 'rail and groove' effect, much like a train rides on its' tracks. As we age, the natural oil and moisture levels decline in the nail plate, and this rail and groove effect becomes apparent. Ridged nails will improve through re-hydration of the nail plate with twice daily applications of a good quality nail and cuticle oil containing Jojoba and Vitamin E."

"Nail textures: Vertical ridges that appear on the nail can indicate disorders as simple as iron deficiency, poor absorption of vitamins and nutrients, overall poor health or they could indicate something as serious as kidney trouble. (So, you see why consulting your physician is so important.) These vertical ridges, as well as bumpy nails, can also suggest that one is prone to developing arthritis. Ridges running horizontally across the nail can indicate physical or mental stress."

(hmm, although I don't trust that as much - looks like a bit of a collection of info without reference as a way of getting advertising revenue... although I have heard about the arthritis thing before)

"Vertical nail ridges, which extend from your cuticle to the tip of your nail, are fairly common and often become more numerous as you age. Vertical ridges in your nails are not a health concern. Although the exact cause of such ridging isn't known, heredity may play a role.

If your fingernails change color or develop horizontal ridges, see your doctor. These changes may indicate underlying health problems, such as respiratory disease, malnutrition or even heart attack."

So the horizontal stripes are more likely to be an issue than the vertical ones ... vertical ones do seem to be about ageing though...

ah so I'm just getting old LOL
Eat plenty of red meat so shouldn't be iron deficient.

As for my horizontal ridges I know mine stem from constantly picking at base... it's a nervous thing... and nailbed got damaged. lso have the discolouring... might have a chat with a GP though, maybe they can think of a miracle cure

Oh dear, I must be getting old! My nails have vertical ridges on them.

Re horizontal ridges, I'm currently living in Africa and it's noticeable when I've been back to the UK that I later have a horizontal stripe on my nails. I put it down to eating a better diet in the UK than here. Some of my nails are also incredibly shiny nowadays. Six of them look as though they have clear polish on them - weird!